After an agent attends a caller he must transfer the call to a survey flow where I need to get the agent's name who attended the call. I've been looking for a achitects variable storing the user name who is transfering the call but there is no such variable. Any ideas?
It's not an architect variable. You will need to use the conversation or analytics APIs. This level of complexity is probably best suited for a middleware service that you consume via a data action. Parsing a conversation object directly in Architect would be pretty gnarly, if it's even possible.